: plzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz help the form was working properly and dunno why that error apears ......suddenly : : here is the code :: : ds=Manager.Select("select max(BOOK_CODE)from BOOK");: double tempbookcode=Convert.ToDouble(ds.Tables[0].Rows[0].ItemArray0].ToString())+1;: this.bCode=tempbookcode.ToString();: : : pleas this is so urgent: